A photo-solidification modeling technique has been developed to fabricate an object having an non-existent three-dimensional shape. This technique utilizes a photo-solidifying liquid having a property of being solidified by light exposure. The photo-solidifying liquid is stored in a liquid vessel, and in a first step, it is exposed to a light at a given part of the liquid surface to form a solidified layer corresponding to a section. Then, in a second step, the solidified layer is immersed. In a third step, the upper surface of the solidified layer is covered (coated) with the unsolidified liquid. The first to the third steps constitute a cycle, which is repeated many times so as to fabricate a three-dimensional object having solidified layers stacked in a unitary structure. The technique is disclosed in Japanese Laid-Open Patent Publication No. 56-144478 and U.S. Pat. No. 2,775,758.
When the immersion depth of the solidified layer in a cycle is large, such immersion of the solidified layer will cause the unsolidified liquid to be introduced onto the upper surface thereof. However, when the immersion depth in a cycle is small, surface tension of the liquid will with such introduction. Various techniques have been proposed to facilitate the process of recoating by the unsolidified liquid.
U.S. Pat. No. 4,575,330 discloses a technique in which a solidified layer is once immersed deeply enough to introduce an unsolidified liquid onto the solidified layer, and then the solidified layer is moved upwardly to reduce the thickness of the unsolidified liquid. According to this technique, however, it takes much time to obtain a quiet liquid surface, which makes it difficult to reduce the time required for recoating.
Japanese Laid-Open Patent Publication No. 61-114818 discloses a technique in which a smooth plate is swept over a solidified layer to force an unsolidified liquid by the front surface of the smooth plate and thereby to introduce the unsolidified liquid onto the solidified layer. In another technique, a brush is used in place of the smooth plate (See Japanese Laid-Open Patent Publication No. 3-246025 filed by the applicant of this application). In this system, however, it is difficult to keep on forcing a sufficient amount of unsolidified liquid over the solidified layer, and consequently a solidified layer having a wide extension will have some portions unrecoated or be left unrecoated at some parts of the surface thereof. In order to prevent this, the smooth plate or brush must be reciprocated many times, resulting in much time required for the recoating process.